Serial plating system

ABSTRACT

A serial plating system includes a plurality of nozzles that are disposed in a plating tank at a position opposite to a plurality of workpieces, and that discharge a plating solution toward the plurality of workpieces, and a plurality of anodes that are disposed in the plating tank at a position opposite to the plurality of workpieces that are serially transferred in the plating tank, one nozzle among the plurality of nozzles and at least one anode among the plurality of anodes being alternately and repeatedly disposed along a transfer direction in which the plurality of workpieces are serially transferred. The plurality of nozzles and the plurality of anodes may be disposed to overlap in a side view along the transfer direction.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No.2011-214302, filed on Sep. 29, 2011, the entirety of which isincorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a serial plating system.

2. Description of the Related Art

A serial plating system is configured so that an electric field isformed between a workpiece (cathode) that is suspended from (held by) atransfer jig and serially transferred in a plating tank, and anelectrode (anode) disposed in the plating tank to plate the platingtarget surface of the workpiece.

A nozzle that discharges a plating solution to the workpiece may beprovided between the workpiece and the electrode (anode plate) (seeJP-A-2000-178784, JP-A-2006-214006, and JP-A-58-6998). In this case, aspace having a dimension equal to or larger than the diameter of thenozzle must be provided between the workpiece and the electrode (anodeplate). JP-A-2006-214006 discloses that the distance between the cathodeand the anode is equal to or more than 100 mm.

JP-A-2006-214006 and JP-A-58-6998 disclose high-speed plating. It isnecessary to increase the current value or the current density ofcurrent that flows between the workpiece and the electrode through theplating solution in order to implement high-speed plating. The currentvalue or the current density may be efficiently increased by reducing acurrent loss by reducing the distance between the workpiece and theelectrode so that the resistance of the plating solution present betweenthe workpiece and the electrode decreases.

However, since the nozzle is disposed between the workpiece and theelectrode (anode plate) in JP-A-2006-214006 and JP-A-58-6998, areduction in distance between the workpiece and the electrode (anodeplate) is limited.

If the electrode (anode plate) is disposed close to the workpiece, aninterference between the nozzle and the anode plate is caused, orflowability of the plating solution becomes worse due to narrowclearance between the nozzle and the anode plate.

SUMMARY

Several aspects of the invention may provide a serial plating systemthat can efficiently the current density of current supplied to theworkpiece by employing a structure that can reduce the distance betweenthe workpiece and the anode without causing interference between thenozzle and the anode.

Several aspects of the invention may provide a serial plating systemthat can prevent a situation in which the plating solution cannot escapefrom the space between the workpiece and the anode as a result ofreducing the distance between the workpiece and the anode, so that freshplating solution discharged from the nozzle cannot come in contact withthe workpiece.

Several aspects of the invention may provide a serial plating systemthat can prevent a situation in which the plating solution cannot escapefrom the space between the workpiece and the anode as a result ofreducing the distance between the workpiece and the anode, so that theworkpiece is drawn toward the nozzle due to a negative-pressure areathat occurs around an area in which the plating solution is dischargedfrom the nozzle at a high speed.

According to one aspect of the invention, there is provided a serialplating system comprising:

a plating tank that holds a plating solution, and plates a plurality ofworkpieces that are serially transferred while being held by a transferjig, and are set to as a cathode;

a plurality of nozzles that are disposed in the plating tank at aposition opposite to the plurality of workpieces, and that discharge theplating solution toward the plurality of workpieces; and

a plurality of anodes that are disposed in the plating tank at aposition opposite to the plurality of workpieces that are seriallytransferred in the plating tank, and

one nozzle among the plurality of nozzles and at least one anode amongthe plurality of anodes being alternately and repeatedly disposed alonga transfer direction in which the plurality of workpieces are seriallytransferred.

According to one aspect of the invention, at least one anode is disposedbetween two nozzles by dividing an anode plate that has been normallydisposed on the back side of a plurality of nozzles. Thus, it is able tocut waste such as having to dispose the anode plate back side of thenozzles opposite to the workpiece, and the plurality of anodes can bedisposed close to the plating target surface of the workpiece. Thismakes it possible to reduce the distance between the plating targetsurface of the workpiece and the anode, and reduce the resistance of theplating solution present between the plating target surface of theworkpiece and the anode, so that the current density of current thatflows between the plating target surface of the workpiece and the anodecan be efficiently increased. The plating thickness of the platingtarget surface of the workpiece per unit time increases (i.e., thethroughput increases) as the current density increases, so thatthrough-holes formed through the workpiece can be efficiently plated.Therefore, a given plating thickness can be achieved without increasingthe total length of the plating tank. This makes it possible to reducethe total length of the serial plating system. Moreover, since thedistance between the plating target surface of the workpiece and theanode can be reduced, it is also possible to reduce the size of theserial plating system in the widthwise direction. Since one nozzle amongthe plurality of nozzles and at least one anode among the plurality ofanodes are alternately and repeatedly disposed, the nozzles to theanodes can be disposed at a sufficient density relative to the workpiecewithout causing worse flowability of the plating solution due to narrowclearance between the nozzle and the anode.

(2) In the serial plating system,

the plurality of nozzles and the plurality of anodes may be disposed tooverlap in a side view along the transfer direction.

According to one aspect of the invention, the plurality of anodes can bedisposed close to the plating target surface of the workpiece to amaximum extent by disposing the plurality of nozzles and the pluralityof anodes to overlap in the side view. This layout is first accomplishedby providing at least one anode between two adjacent nozzles, but isnever accomplished by a conventional anode that has been normally formedto have a given length and disposed on the back side of a plurality ofnozzles opposite to the workpiece.

(3) In the serial plating system,

each of the plurality of anodes may have a profile so that a distancefrom a plating target surface of each of the plurality of workpiecesincreases as a distance from an electrode centerline that divides eachof the plurality of anodes into two parts in a plan view andperpendicularly intersects the transfer direction increases.

If the anode has a rectangular profile in a plan view, since thedistance between the plating target surface of the tabular workpiece andthe anode is constant, the plating solution discharged from the nozzleis concentrated (trapped) in a narrow range corresponding to theconstant distance. In this case, fresh plating solution discharged fromthe nozzle cannot come in contact with the workpiece, and the workpiecemay be drawn toward a negative-pressure area that occurs around thenozzle stream. According to the above configuration, the distancebetween the plating target surface of the workpiece and the anodeincreases as the distance from the centerline of the anode increases, sothat the plating solution can escape from the space between theworkpiece and the anode through a wider clearance between the nozzle andthe anode.

(4) In the serial plating system,

each of the plurality of anodes may have a curved horizontalcross-sectional profile.

Thus, each of the plurality of anodes may have a curved horizontalcross-sectional profile having an elliptical or a circular horizontalinstead of crossing two lines at a corner.

(5) In the serial plating system,

each of the plurality of anodes may have a circular horizontalcross-sectional profile. It is preferable that the anode have a circularhorizontal cross-sectional profile rather than an elliptical horizontalcross-sectional profile as long as the horizontal cross-sectional areais identical in order to dispose the anode closer to the plating targetsurface of the workpiece while preventing interference with the nozzle.

(6) In the serial plating system,

each of the plurality of anodes may be an insoluble anode. Either one ofan soluble anode and a insoluble anode may be applied to be the anode.The soluble anode of which the electrode component is dissolved in theplating tank is consumed rapidly when the current density is increased.In contrast, the insoluble anode does not pose a problem even if thecurrent density is increased.

(7) In the serial plating system,

each of the plurality of nozzles may have a circular horizontalcross-sectional profile having a diameter that is smaller than adiameter of a horizontal cross section of each of the plurality ofanodes. The anode can be disposed closer to the plating target surfaceof the workpiece while preventing interference with the circular(chamfered) nozzle.

(8) In the serial plating system,

a center of a horizontal cross section of each of the plurality ofnozzles may be disposed at a position closer to the plating targetsurface of each of the plurality of workpieces as compared with a centerof the horizontal cross section of each of the plurality of anodes.Specifically, the center of the horizontal cross section of each of theplurality of nozzles and the center of the horizontal cross section ofeach of the plurality of anodes are not disposed along a straight linethat extends along the transfer direction, but are disposed in astaggered arrangement. This makes it possible to easily provide aminimum interval between the nozzle and the anode that are adjacent toeach other as compared with the case where the center of the nozzle andthe center of the anode are disposed along a straight line.Specifically, interference with the nozzle can be easily prevented whilemaximizing the diameter of the anode.

(9) In the serial plating system,

a first minimum distance δ1 from each of the plurality of nozzles to theplating target surface of each of the plurality of workpieces may beless than a second minimum distance 62 from each of the plurality ofanodes to the plating target surface of each of the plurality ofworkpieces, and

an outer diameter of each of the plurality of nozzles may be less thanthe second minimum distance δ2. This makes it possible to dispose thenozzle closer to the workpiece as compared with the anode, and makes itunnecessary to increase the supply pressure of the plating solution. Itis also possible to prevent a situation in which the plating solutionthat is discharged from the nozzle to the workpiece at a given sprayangle in a plan view is blocked by the anode. Since the curvature of thenozzle can be increased by setting the diameter of the nozzle that isdisposed close to the workpiece to be less than the second minimumdistance δ2 between the anode and the workpiece, it is possible toeasily provide an escape space for the plating solution.

(10) In the serial plating system,

a third minimum distance δ3 between each of the plurality of anodes andeach of the plurality of nozzles may be less than the second minimumdistance δ2. This makes it possible to dispose the anode closer to theplating target surface of the workpiece. Note that the plating solutiondischarged from the nozzle toward the workpiece can escape from thespace between the nozzle (anode) and the workpiece into the wide spacepresent in the plating tank through the space between the nozzle and theanode that are adjacent to each other. This makes it possible to allowthe workpiece to always come in contact with fresh plating solution.

(11) In the serial plating system,

the third minimum distance δ3 may be equal to or greater than the firstminimum distance δ1. According to the above configuration, since theflow resistance of the space between the nozzle and the anode is equalto or less than the flow resistance of the space between the workpieceand the nozzle, the plating solution can easily escape into the widespace present in the plating tank through the space between the nozzleand the anode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating a serial platingsystem according to one embodiment of the invention;

FIG. 2 is a schematic plan view illustrating the serial plating systemillustrated in FIG. 1;

FIGS. 3A to 3C are horizontal cross-sectional views illustrating ananode;

FIG. 4 is a view illustrating the relationship between a first minimumdistance, a second minimum distance, and a third minimum distance;

FIG. 5A is a view illustrating an example in which the center of anozzle and the center of an anode are disposed along a straight line,and FIG. 5B is a view illustrating an example in which a plurality ofanodes are disposed between two nozzles; and

FIG. 6 is a view illustrating an example in which an anode has arectangular horizontal cross-sectional profile.

DESCRIPTION OF EXEMPLARY EMBODIMENT(S)

Exemplary embodiments of the invention are described in detail below.Note that the following exemplary embodiments do not in any way limitthe scope of the invention defined by the claims laid out herein. Notethat all of the elements described in connection with the followingexemplary embodiments should not necessarily be taken as essentialelements of the invention.

1. Overall Configuration

FIG. 1 is a cross-sectional view illustrating a serial plating systemaccording to one embodiment of the invention, and FIG. 2 is a plan viewillustrating the serial plating system. As illustrated in FIG. 1, aplating tank 10 is configured so that a workpiece 1 that is suspendedfrom (held by) a transfer jig 20 is immersed in a plating solution 2 toplate the workpiece 1. The plating tank 10 has a peripheral wall 10A anda bottom wall 10B, and holds the plating solution 2 up to a liquid levelL.

The workpiece 1 is a circuit board, a flexible circuit board, or thelike, and each side of the workpiece 1 is plated, for example. Thetransfer jig 20 serially transfers the workpiece 1, and supplies currentto the workpiece 1. The workpiece 1 serves as a cathode. Morespecifically, a power-feeding section that may be a transfer rail andcomes in sliding contact with the transfer jig 20 is connected to anegative terminal of a power supply, and current is supplied to theworkpiece 1 via the power-feeding section and the transfer jig 20.

The workpiece 1 that is suspended from (held by) the transfer jig 20 isserially transferred along a transfer direction A illustrated in FIG. 2(i.e., along the depth direction in FIG. 1). A chain that iscontinuously driven using a sprocket, a cylinder, and the like may beused as a means that serially transfers the workpiece 1. The transferjig 20 holds one workpiece 1. As illustrated in FIG. 2, a plurality ofworkpieces 1 are serially transferred in the plating tank 10. When theworkpiece 1 is a rigid body (e.g., circuit board), the transfer jig 20can hold the workpiece 1 in a suspended state by chucking the upper endof the workpiece 1. When the workpiece 1 is a flexible body (e.g.,flexible circuit board), the transfer jig 20 chucks the upper end andthe lower end of the workpiece 1 using a frame. FIG. 1 illustrates anupper frame 20A and a lower frame 20B of the transfer jig 20.

As illustrated in FIGS. 1 and 2, a plurality of nozzles 30 that aredisposed at a position opposite to the workpiece 1, and that dischargethe plating solution to the workpiece 1 are provided in the plating tank10. In one embodiment of the invention in which each side of theworkpiece 1 is plated, the nozzles 30 are disposed on each side of theserial transfer path of the workpiece 1 (i.e., disposed in two rows).The upper end of each nozzle 30 is closed, and the lower end of eachnozzle 30 communicates with a supply channel of a plating solutionsupply section 11 that is provided at the bottom of the plating tank 10.A perforated plate 11A may be provided in the middle of the supplychannel of the plating solution supply section 11.

A plurality of nozzle holes (not illustrated in the drawings) are formedin the side of the nozzle 30 that faces the workpiece 1 at intervals inthe vertical direction. A fresh plating solution that has been suppliedto the nozzle 30 from the plating solution supply section 11 isdischarged to the plating target surface of the workpiece 1 from eachnozzle hole at a given spray angle. Note that the nozzle 30 is formed ofan insulator, and does not adversely affect an electric field that isapplied to the workpiece 1.

The lower end of the nozzle 30 is secured on the plating solution supplysection 11. An upper end-securing section 31 is secured on the upper endof the nozzle 30. The upper end-securing section 31 is secured on a beammember 32 that extends in the transfer direction A inside the platingtank 10. The beam member 32 is supported on the peripheral wall 10A ofthe plating tank 10 via a beam support member 33.

A plurality of anodes 40 are provided in the plating tank 10, theplurality of anodes 40 being disposed at a position opposite to theworkpieces that are serially transferred in the plating tank 10. Theanodes 40 are disposed on each side of the serial transfer path of theworkpiece 1 (i.e., disposed in two rows) for the reason described abovein connection with the nozzles 30. Each anode 40 is connected to apositive terminal of a power supply (not illustrated in the drawings).Note that each power supply that is connected to one anode 40 canindependently control the current value.

An insulating section (e.g., insulating caps 41 and 42) may be disposedon each end (upper end and lower end) of the anode 40. The insulatingcap 41 that is disposed on the lower end of the anode 40 is secured onthe plating solution supply section 11 via a mounting section 43. Theinsulating caps 41 and 42 define an electric field region in thevertical direction by insulating the upper end and the lower end of theanode 40. An electrode lead section 44 that is electrically connected tothe anode 40 is provided to the insulating cap 42 that is disposed onthe upper end of the anode 40. Each electrode lead section 44 that isconnected to each anode 40 extends upward beyond the liquid level L inthe plating tank 10, and is connected to a common electrode 45. Notethat each electrode lead section 44 may be connected to a correspondingpower supply so that the current value of each anode 40 can beindependently controlled. The insulating caps 41 and 42 may beconfigured so that the vertical position thereof can be adjustedcorresponding to the size of the workpiece 1.

A mask member 50 may be provided directly under the workpiece 1. Themask member 50 has a groove that is formed along the transfer directionA (see FIG. 2). The lower end of the workpiece 1 may be inserted intothe groove of the mask member 50 to mask the lower end of the workpiece1. In one embodiment of the invention, the lower frame 20B of thetransfer jig 20 is inserted into (masked by) and guided by the groove ofthe mask member 50. Note that the vertical position of the mask member50 can be adjusted corresponding to the size of the workpiece 1.

2. Positional Relationship Between Nozzle and Anode

In one embodiment of the invention, a plurality of nozzles 30 and aplurality of anodes 40 are alternately disposed along the transferdirection A in which a plurality of workpieces 1 are seriallytransferred (see FIG. 2). This makes it possible to dispose the nozzles30 and the anodes 40 at an sufficient (appropriate) density relative tothe plating target surface of the workpiece 1. At least one anode 40 isdisposed between two adjacent nozzles 30 that are disposed at anappropriate interval in a plan view. The arrangement pitch of thenozzles 30 may be set to 60 to 90 mm, for example. The serial platingsystem according to one embodiment of the invention is thuscharacterized in that at least one anode 40 (one anode 40 in FIG. 2) isdisposed between two nozzles by dividing an anode that has been normallyformed to have a given length and disposed on the back side of aplurality of nozzles 30 opposite to the workpiece 1.

Specifically, a plurality of anodes 40 can be disposed close to theplating target surface of the workpiece 1 to such an extent thatinterference with each nozzle 30 does not occur (see FIG. 1). Therefore,since the distance between the plating target surface of the workpiece 1and the anode 40 can be reduced, the current density between the platingtarget surface of the workpiece 1 (cathode) and the anode 40 increases.The plating thickness of the plating target surface of the workpiece 1per unit time increases as the current density increases. Therefore, agiven plating thickness can be achieved without increasing the totallength of the plating tank 10. This makes it possible to reduce thetotal length of the serial plating system. Moreover, since the distancebetween the plating target surface of the workpiece 1 and the anode 40can be reduced, it is also possible to reduce the size of the serialplating system in the widthwise direction.

In one embodiment of the invention, the anodes 40 can be disposed closeto the plating target surface of the workpiece 1 to a maximum extent bydisposing the nozzles 30 and the anodes 40 to overlap in a side view(FIG. 1) along the transfer direction A (see FIG. 2). This layout isfirst accomplished by providing at least one anode 40 between twoadjacent nozzles 30, but is never accomplished by a conventional anodethat has been normally formed to have a given length and disposed on theback side of a plurality of nozzles 30 opposite to the workpiece 1.

3. Profile of Anode

The horizontal cross-sectional profile of the nozzle 30 and the anode 40is not particularly limited. However, it is preferable to ensure thatthe plating solution that has been discharged from the nozzle 30 towardthe workpiece 1 can escape from the space between the plating targetsurface of the workpiece 1 and the anode 40 since the distance betweenthe plating target surface of the workpiece 1 and the anode 40 isreduced.

For example, each anode 40 may be formed to have a curved profile sothat the distance from the plating target surface of each workpiece 1increases as the distance from an electrode centerline B that divideseach anode 40 into two parts in a plan view and perpendicularlyintersects the transfer direction A increases (see FIG. 2). For example,each anode 40 may have a curved horizontal cross-sectional profile (seeFIG. 2) without having any corners. Note that each anode 40 may have anelliptical horizontal cross-sectional profile or the like. If each anode40 has a rectangular profile in a plan view, the distance between theplating target surface of the tabular workpiece and each anode 40 isconstant. Therefore, the plating solution discharged from the nozzle 30is trapped in a narrow range corresponding to the constant distance andis hard to escape through a narrow clearance between the nozzle 30 andthe anode 40. According to one embodiment of the invention, since thedistance between the plating target surface of the workpiece 1 and theanode 40 increases as the distance from the electrode centerline Bincreases, the plating solution can escape from the space between theplating target surface of the workpiece 1 and the anode 40 through awider clearance between the nozzle 30 and the anode 40. Note that it ispreferable that each anode 40 have a circular horizontal cross-sectionalprofile rather than an elliptical horizontal cross-sectional profile aslong as the horizontal cross-sectional area is identical in order todispose the center of each anode 40 closer to the plating target surfaceof the workpiece 1 while preventing interference with each nozzle 30.

When each anode 40 has a curved horizontal cross-sectional profile, thedistance between the workpiece and the anode differs depending on theprofile position of the anode. However, since the workpiece 1 isserially transferred, the plating thickness can be made uniform in theserial transfer direction A of the workpiece 1. Accordingly, thein-plane uniformity of the plating thickness of the workpiece 1 can beensured by managing the perpendicularity and the like of the anode 40 sothat a non-uniform plating thickness distribution does not occur in thevertical direction of the workpiece 1.

4. Structure of Anode

A soluble anode or an insoluble anode may be used as the anode 40. Thesoluble anode is formed so that the electrode material is dissolved andserves as a plating component. The soluble anode is consumed, and mustbe exchanged. Note that the soluble anode has a drawback in that itcontains impurities (e.g., phosphorus (P)) in addition to the platingcomponent. The insoluble anode is formed so that the electrode materialis not dissolved. When using the insoluble anode, metal ions (e.g.,cupric oxide) present in the plating solution contained in the platingtank 10 serve as a plating component, and the insoluble anode is merelyused as an electrode. In one embodiment of the invention, it ispreferable to use the insoluble anode as the anode 40. In particular,when achieving a high current density of 10 to more than 10 A/dm2, forexample, the soluble anode is consumed rapidly. Therefore, it ispreferable to use the insoluble anode as the anode 40.

As illustrated in FIG. 3A, the anode 40 that is formed using theinsoluble anode may include an anode main body 40A that is positioned onthe center side, and is formed of a metal, an alloy, or the like, and apartition 40B that covers the anode main body 40A. The anode main body40A is formed in the shape of a hollow tube in order to reduce theweight of the anode 40. Note that the anode main body 40A may be formedin the shape of a solid rod. The partition 40B is formed of a materialthat does not block an electric field (electrons), and does not allowthe plating solution to pass through. The partition 40B isolates theanode main body 40A positioned on the center side from the platingsolution. The partition 40B thus allows the anode 40 to function as aninsoluble anode. In this case, at least the partition 40B has a circularhorizontal cross-sectional profile. It is preferable that the partition40B be disposed at a distance from the anode main body 40A. This isbecause it is necessary to provide a space that accommodates gasgenerated from the anode main body 40A. The lower end of the partition40B that is immersed in the plating solution contained in the platingtank 10 is liquid-tightly and air-tightly sealed. The upper end of thepartition 40B may be open to the atmosphere.

When the partition 40B that is flexible and does not have a shaperetention capability is disposed at a distance from the anode main body40A, a shape retention member 40C may be disposed between the anode mainbody 40A and the partition 40B (see FIG. 3B). The partition 40B exhibitsa shape retention capability by being secured on the shape retentionmember 40C. As illustrated in FIG. 3C, a plurality of spacer members 40Dmay be disposed between the anode main body 40A and the shape retentionmember 40C in order to separate the partition 40B from the anode mainbody 40A.

5. Profile of Nozzle

Since the cross-sectional area of the nozzle 30 is normally smaller thanthat of the anode 40, the horizontal cross-sectional profile of thenozzle 30 is less restricted as compared with the anode 40. The nozzle30 may have a rectangular horizontal cross-sectional profile. Note thatit is preferable that the nozzle 30 have a chamfered profile in order todispose the anode 40 closer to the plating target surface of theworkpiece 1 while preventing interference with each nozzle 30. In oneembodiment of the invention, each nozzle 30 has a circular horizontalcross-sectional profile having a diameter D1 that is smaller than thediameter D2 of the horizontal cross section of each anode 40.

6. Detailed positional relationship between nozzle and anode in planview

As illustrated in FIGS. 2 and 4, the center P1 of the horizontal crosssection of each nozzle 30 may be disposed at a position closer to theplating target surface of each workpiece 1 as compared with the centerP2 of the horizontal cross section of each anode 40.

Specifically, the center P1 of the horizontal cross section of eachnozzle 30 and the center P2 of the horizontal cross section of eachanode 40 may be disposed in a staggered arrangement (see FIGS. 2 and 4).Note that the center P1 of the horizontal cross section of each nozzle30 and the center P2 of the horizontal cross section of each anode 40may be disposed along a straight line L1 along the transfer direction A(see FIG. 5A). The above configuration makes it possible to easilyprevent interference with the nozzle 30 while maximizing the diameter D2of each anode 40 that is disposed between two adjacent nozzles 30 ascompared with the case where the center P1 of the horizontal crosssection of each nozzle 30 and the center P2 of the horizontal crosssection of each anode 40 are disposed along the straight line L1 (seeFIG. 5A).

As illustrated in FIG. 5B, a plurality of anodes 40 may be disposedbetween two nozzles 30 (i.e., an example in which at least one anode 40is disposed between two nozzles 30). In FIG. 5B, the center P1 of thehorizontal cross section of each nozzle 30 is disposed at a positioncloser to the plating target surface of each workpiece 1 as comparedwith the center P2 of the horizontal cross section of each anode 40 inthe same manner as in FIG. 4. If the arrangement pitch of the nozzles 30is identical in FIGS. 4 and 5B, it is necessary to reduce the diameterD2 of the anode 40 in FIG. 5B as compared with FIG. 4. If the diameterD2 of the anode 40 is identical in FIGS. 4 and 5B, the arrangement pitchof the nozzles 30 must be increased in FIG. 5B as compared with FIG. 4.Therefore, the layout illustrated in FIG. 4 is better than thatillustrated in FIG. 5B.

In one embodiment of the invention, a first minimum distance δ1 fromeach nozzle 30 to the plating target surface of each workpiece 1 may beset to be less than a second minimum distance δ2 from each anode 40 tothe plating target surface of each workpiece 1 (δ1<δ2), and the outerdiameter D1 of each nozzle 30 may be set to be less than the secondminimum distance δ2 (D1<δ2) (see FIG. 4). The first minimum distance Mmay be set to 10 mm≦δ1≦20 mm, and the second minimum distance δ2 may beset to 15 mm≦δ2≦35 mm, for example.

This makes it possible to dispose the nozzle 30 closer to the workpiece1 as compared with the anode 40, and makes it unnecessary to increasethe supply pressure of the plating solution. It is also possible toprevent a situation in which the plating solution that is dischargedfrom the nozzle 30 to the workpiece 1 at a given spray angle in a planview is blocked by the anode 40.

Since the curvature of the nozzle 30 can be increased by setting thediameter D1 of the nozzle 30 that is disposed close to the workpiece 1to be less than the second minimum distance δ2 between the anode 40 andthe workpiece 1, it is possible to easily provide an escape space forthe plating solution.

When the minimum distance M between the nozzle 30 and the workpiece 1 isset to 10 mm≦δ1≦20 mm, for example, the speed of a jet nozzle streamthat is discharged from the nozzle 30 and reaches the workpiece 1increases. Since the area of the jet nozzle stream is pressurized, anegative-pressure area may occur around the area of the jet nozzlestream. Since a plurality of nozzle holes are formed in the nozzle 30 atintervals in the vertical direction, a negative-pressure area is formedbetween two nozzle holes.

If the flow of the plating solution between the workpiece 1 and thenozzle 30 (anode 40) is insufficient, the plating solution may not enterthe negative-pressure area. In particular, a flexible workpiece 1 may bedrawn toward the nozzle 30. Therefore, it is important to ensure thatthe plating solution discharged from the nozzle 30 can escape from thespace between the workpiece 1 and the anode 40 in order to prevent aphenomenon in which the workpiece 1 is drawn toward thenegative-pressure area.

As illustrated in FIG. 6, the anode 40 may have a horizontalcross-sectional profile (e.g., rectangular horizontal cross-sectionalprofile) other than a circular horizontal cross-sectional profile. InFIG. 6, the relationships “δ1<δ2” and “D1<δ2” are satisfied. When theanode 40 has a rectangular horizontal cross-sectional profile (see FIG.6), since the entire long side of the anode 40 is positioned at thesecond minimum distance δ2 from the workpiece 1, and the anode 40 hascorners that are not chamfered, the escape space for the platingsolution is narrow as compared with the layout illustrated in FIG. 4.Therefore, the layout illustrated in FIG. 4 is better than thatillustrated in FIG. 6.

In one embodiment of the invention, a third minimum distance δ3 betweeneach anode 40 and each nozzle 30 may be set to be less than the secondminimum distance δ2 from each anode 40 to the plating target surface ofeach workpiece 1 (δ3<δ2). This makes it possible to dispose the anode 40closer to the plating target surface of the workpiece 1. Note that theplating solution discharged from the nozzle 30 toward the workpiece 1can escape from the space between the nozzle 30 (anode 40) and theworkpiece 1 into the wide space present in the plating tank 10 throughthe space between the nozzle 30 and the anode 40 that are adjacent toeach other. This makes it possible to allow the workpiece 1 to alwayscome in contact with fresh plating solution, and prevents a situation inwhich the workpiece 1 is drawn toward the negative-pressure area.

The third minimum distance δ3 between each anode 40 and each nozzle 30may be set to be greater than or equal to the first minimum distance δ1from each nozzle 30 to the plating target surface of each workpiece 1(δ3≧δ1). In this case, since the flow resistance of the space betweenthe nozzle 30 and the anode 40 is equal to or less than the flowresistance of the space between the workpiece 1 and the nozzle 30, theplating solution can easily escape into the wide space present in theplating tank 10 through the space between the nozzle 30 and the anode40.

Although only some embodiments of the invention have been described indetail above, those skilled in the art would readily appreciate thatmany modifications are possible in the embodiments without materiallydeparting from the novel teachings and advantages of the invention.Accordingly, such modifications are intended to be included within thescope of the invention. Any term cited with a different term having abroader meaning or the same meaning at least once in the specificationand the drawings can be replaced by the different term in any place inthe specification and the drawings.

Although the invention has been described using specific terms, devices,and/or methods, such description is for illustrative purposes of thepreferred embodiment(s) only. Changes may be made to the preferredembodiment(s) by those of ordinary skill in the art without departingfrom the scope of the present invention. In addition, it should beunderstood that aspects of the preferred embodiment(s) generally may beinterchanged in whole or in part.

What is claimed is:
 1. A serial plating system comprising: a platingtank that holds a plating solution, and plates a plurality of workpiecesthat are serially transferred while being held by a transfer jig, andare set to as a cathode; a plurality of nozzles that are disposed in theplating tank at a position opposite to the plurality of workpieces, andthat discharge the plating solution toward the plurality of workpieces;and a plurality of anodes that are disposed in the plating tank at aposition opposite to the plurality of workpieces that are seriallytransferred in the plating tank, and one nozzle among the plurality ofnozzles and at least one anode among the plurality of anodes beingalternately and repeatedly disposed along a transfer direction in whichthe plurality of workpieces are serially transferred.
 2. The serialplating system as defined in claim 1, the plurality of nozzles and theplurality of anodes being disposed to overlap in a side view along thetransfer direction.
 3. The serial plating system as defined in claim 1,each of the plurality of anodes having a horizontal cross-sectionalprofile so that a distance from a plating target surface of each of theplurality of workpieces increases as a distance from an electrodecenterline that divides each of the plurality of anodes into two partsin a plan view and perpendicularly intersects the transfer directionincreases.
 4. The serial plating system as defined in claim 3, each ofthe plurality of anodes having a curved horizontal cross-sectionalprofile.
 5. The serial plating system as defined in claim 3, each of theplurality of anodes having a circular horizontal cross-sectionalprofile.
 6. The serial plating system as defined in claim 1, each of theplurality of anodes being an insoluble anode.
 7. The serial platingsystem as defined in claim 1, each of the plurality of nozzles having acircular horizontal cross-sectional profile having a diameter that issmaller than a diameter of a horizontal cross section of each of theplurality of anodes.
 8. The serial plating system as defined in claim 1,a center of a horizontal cross section of each of the plurality ofnozzles being disposed at a position closer to the plating targetsurface of each of the plurality of workpieces as compared with a centerof a horizontal cross section of each of the plurality of anodes.
 9. Theserial plating system as defined in claim 8, a first minimum distance δ1from each of the plurality of nozzles to the plating target surface ofeach of the plurality of workpieces being less than a second minimumdistance δ2 from each of the plurality of anodes to the plating targetsurface of each of the plurality of workpieces, and an outer diameter ofeach of the plurality of nozzles being less than the second minimumdistance δ2.
 10. The serial plating system as defined in claim 9, athird minimum distance δ3 between each of the plurality of anodes andeach of the plurality of nozzles being less than the second minimumdistance δ2.
 11. The serial plating system as defined in claim 10, thethird minimum distance δ3 being equal to or greater than the firstminimum distance δ1.